The present invention relates to an improved system and method for heating biological tissue via RF energy and, more particularly, to a system and method which rely upon a single electrode. Control of phase and pulse width modulation of applied RF waves obviates the need for cooling of the skin surface, to facilitate efficient beating of underlying layers of tissue such as dermis and subcutaneous layers. Specifically, heating and contraction of adipose tissues as a means of cellulite reduction is achieved.
Adipose tissues, particularly cellulite, are typically treatable only with a strict regimen of diet and exercise. Patient compliance with these previously available regimens is poor. Cellulite occurs when fat cells swell compressing the flow of blood and lymph. This leads to build-up of fluid and toxins. Connective tissue forms hard fibrous capsules around the fat cells. This results in a “lumpy” appearance. The fat cells involved are located primarily in the third and most deep (skin) layer, which has a variable by thickness depending on the amount fat in the subject. Thickness of this layer typically increases in areas such as abdomen, thighs and buttocks.
Previously proposed methods for cellulite treatment include Topical treatment, Teas and capsules, Cellulite wraps, Endermologie, Mesotherapy, Acthyderm and Ultrasonic and particularly focused ultrasonic treatment. These techniques have demonstrated various degrees of clinical efficacy in reducing the “lumpy” appearance associated with cellulite deposits. In addition, thermotherapy using electromagnetic radiation or radio-frequency (RF) waves has been proposed. RF treatment is more effective than other available therapy regimens since it permits the body to heal itself. Non-invasive electromagnetic radiation, including radio-frequency waves, has been proposed in the prior art for treatment of fat and cellulite in addition to use for contraction of collagen, such as involved in the treatment of wrinkles.
The typical RF technique for heating of biological tissues involves exposing the tissue to RF voltage, which produces RF conductive current through the tissue at a level sufficient to overcome the tissue resistance. The current heats the tissue. This method causes uneven heat accompanied by burning of the outer layer(s) the skin. As a result, many of the conventional systems for implementation of this method share, as an inherent disadvantage, a strict requirement for a cooling mechanism to remove an excessive heat of the skin during the treatment.
One example of a prior art system(s) is disclosed in U.S. Pat. No. 6,662,054 assigned to Syneron Medical Ltd. This patent teaches deforming the skin so that a region of skin protrudes from the surrounding skin, and applying RF energy to the protruded skin. The system includes one or more RF electrodes, configured to apply conducted RF current to the skin, and a skin deformer, so that a region of skin protrudes out from surrounding skin and is exposed to the conducted RF current, which follows the deforming act. Teachings of this include a strict requirement for cooling of the skin to prevent burning.
US Patent Application No. 20040002705 assigned to Thermage, Inc. also discloses a system that requires cooling of skin to prevent burning. In particular, this published patent application teaches a method of creating a tissue effect by delivering electromagnetic energy through a skin surface from an electromagnetic energy delivery device coupled to an electromagnetic energy source.
Further additional examples of prior art systems which require cooling of the skin to prevent burning include those disclosed in US Patent Application No. 2004030332 and U.S. Pat. No. 5,919,219 assigned to Thermage, Inc., which teach a system and method for providing treatment to a skin surface by applying RF energy through the skin using a memory for gathering information. These systems include express requirements for a cooling lumen for receiving cooling fluid and a number of RF electrodes. The RF electrodes are provided to transfer RF current to the skin and are configured to be capacitive coupled to the skin surface, thus creating a heating effect through RF conducted current.
In summary, the above-described prior art methods require the use of a separate cooling system to cool the outer skin layer throughout the RF treatment. Further, many of the previously available solutions require a memory unit to store local information pertaining to the treated area throughout the treatment. Further, many of the previously available solutions require extensive preliminary adjustments, such as local impedance matching, prior to each treatment. Further, despite use of the phrase “one or more electrodes in many prior art documents, the above-described alternatives share, a strict requirement for a return electrode pad to be placed against the patient to receive the RF currents after passing tissue being treated. This return electrode for volumetric treatment of adipose tissue (e.g. cellulite) routes a majority of energy through blood and lymphatic vessels. Fat cells are heated only by heat dissipated from these non-target tissues as a result of their inherent resistance.
There is thus a widely recognized need for, and it would be highly advantageous to have, an improved system and method for heating biological tissue via RF energy that attempts to address one or more of the limitations of the above-described systems.